Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$143.92	4.770%	$150.785	$150.79	$150.80	$150.80
Purchase #2	$64.58	11.336%	$71.9008	$71.90	$71.90	$71.90
Purchase #3	$83.98	4.670%	$87.9019	$87.90	$87.90	$87.90
Purchase #4	$11.34	4.798%	$11.8841	$11.88	$11.90	$11.90
Purchase #5	$215.84	11.460%	$240.5753	$240.58	$240.60	$240.60
Purchase #6	$166.60	8.125%	$180.1363	$180.14	$180.15	$180.10
Purchase #7	$238.57	13.536%	$270.8628	$270.86	$270.85	$270.90
7 purchase totals =	$924.83		$1,014.0462	$1,014.05	$1,014.10	$1,014.10